The A409 is a road of two distinct halves. It starts tamely enough, east of Harrow town centre at a large roundabout, notable firstly for being a TOTSO for that strange collection of signposts known as the A404 (which you have to "turn off to stay on" at least nine times in Greater London alone), and more distinctively, because it has the Metropolitan Line running through the middle of it. It begins life as a wide (4 lane) single carriageway road, with occasional centre islands to separate the opposing traffic flows. Sometimes the lanes are all-purpose, occasionally the left hand lane in one or other direction is a bus lane. The area is typically suburban in character, pockets of retail interspersed with older residential development.
Harrow - Bushey Heath
Through suburban Harrow the A409 passes, to arrive at a recently (1996) remodelled layout called George Gange Way, allowing us to avoid Wealdstone High Street, and its station on the main railway line out of Euston. (The station is called "Harrow & Wealdstone", but is in fact firmly in the latter). We cross the railway (the station is also the Bakerloo Line terminus) on a high-level bridge, then we cross another local road before descending steeply to a junction with Palmerston Road. We pass Wealdstone's pretty clock tower, and a couple of nice churches, but although we lose the two lanes in each direction, it is all still very suburban (1930s semis) until we pass Harrow Weald bus garage, where you will see Bus Stands marked on the carriageway, rather than the more usual Bus Stops.
Suddenly the road starts to climb and we are in the country. At a roundabout (there is no flag sign at the roundabout to confirm you are heading in the right direction), we cross the A410 Uxbridge Road (although it stops long before reaching Uxbridge) and continue climbing to Harrow Weald Common which is actually rather wooded. As we are out of the built-up area, there is an increase in speed limit to 40mph. Here, the few houses are, in estate-agent speak, substantial.
We enter a new 30mph limit in time for the traffic signals in Bushey Heath. Strange to think that, had it not been for postwar Green Belt legislation, London Underground's Northern Line would have reached here. The road we cross here is now the A4140, but was once the main road from London to Watford and Birmingham (the A41). The 1922 listing shows the A409 as running only to here. On the afternoon I (Simon) drove this route, we were held up for a long while at the signals. Straight over the crossroads onto Magpie Hall Road, we next pass Stanmore Common, where we come to a TOTSO (it's a mini-roundabout) with a minor road, where we turn left onto Heathbourne Road, passing a large BUPA hospital ("no A&E", the signs say) as we descend to a junction with the A411 Elstree Road which marks the end of the road.
When the A409 was extended beyond the ex-A41 in the 1930s, it used to continue further beyond the A411 further two miles to meet the A41 (former A500) North Western Avenue. This has been severed by the M1 which runs parallel to the A41, so to make further progress northwards it is now necessary first to descend eastwards on the A411 to pass under the M1 and meet the A41.